Human Blood Composition and Tests

Blood Composition

• Blood is a fluid connective tissue
• Plasma is the non-living fluid matrix
• Formed elements are the living blood cells
• Erythrocytes (red blood cells) are the most numerous formed element
• Leukocytes (white blood cells) are crucial for immunity
• Platelets are cell fragments important for blood clotting

Major Components of Whole Blood

• Whole blood is withdrawn and placed in a tube
• Centrifuging separates the components
• Plasma makes up 55% of whole blood, the least dense component
• Buffy coat contains leukocytes and platelets (less than 1%)
• Erythrocytes make up 45% of whole blood, the most dense component

Blood Tests

• Hematocrit measures the percentage of red blood cells in blood.
• Normal hematocrit values differ between males and females.
• Lower RBC count can indicate anemia.
• Anemia is a condition where cells are not able to divide properly due to a lack of vitamin B12.
• RECTAL CANCER could potentially be triggered by a microscopic deficiency of vitamin B12.

Blood Plasma Composition

• Plasma is mostly water (~90%)
• Over 100 dissolved solutes (nutrients, gases, hormones, wastes, proteins, inorganic ions)
• Plasma proteins are the most abundant solutes
• Proteins produced primarily by the liver.
• Albumin is the most abundant protein, maintaining plasma osmotic pressure.

Plasma Proteins

• Albumin: 60% of plasma proteins, key for osmotic pressure and transport
• Globulins (alpha, beta, gamma): transport proteins (36%), involved in immune response and transport of lipids and vitamins.
• Fibrinogen: 4% of plasma proteins, essential for blood clotting.

Formed Elements

• Composed of complete cells (WBCs) and cell fragments (platelets)
• RBCs lack nuclei and organelles
• Most formed elements survive in blood for few days and do not divide.
• All are made in bone marrow.
• Important cells for immunity and defense against diseases.
• Leukocytes (WBCs) make up less than 1% of whole blood
• There are different types of Leukocytes, each with specific functions
• Crucial for immunity and defense
• Function in defense against diseases and chronic infections.
• Granulocytes: visible granules (neutrophils, eosinophils, basophils)
• Agranulocytes: no visible granules (lymphocytes, monocytes)

Erythrocytes (Red Blood Cells)

• Specialized for gas transport
• Packed with hemoglobin
• Biconcave shape for maximizing surface area for oxygen uptake
• Anucleated and lack most organelles, maximizing space for hemoglobin
• Normal values differ between males and females

Anemia

• Abnormally low oxygen-carrying capacity of blood.
• Causes include blood loss, decreased RBC production, or increased RBC destruction
• Three main types of anemia based on cause: blood loss, low RBC production, high RBC destruction